Characterization of the mouse Dazap1 gene encoding an RNA-binding protein that interacts with infertility factors DAZ and DAZL.

Dai T, Vera Y, Salido EC, Yen PH - BMC Genomics (2001)

Bottom Line:
Although a majority of DAZAP1 is present in the cytoplasmic fraction, they are not associated with polyribosomes.Its predominant expression in testes suggests a role in spermatogenesis.Its subcellular localization indicates that it is not directly involved in mRNA translation.

Background: DAZAP1 (DAZ Associated Protein 1) was originally identified by a yeast two-hybrid system through its interaction with a putative male infertility factor, DAZ (Deleted in Azoospermia). In vitro, DAZAP1 interacts with both the Y chromosome-encoded DAZ and an autosome-encoded DAZ-like protein, DAZL. DAZAP1 contains two RNA-binding domains (RBDs) and a proline-rich C-terminal portion, and is expressed most abundantly in the testis. To understand the biological function of DAZAP1 and the significance of its interaction with DAZ and DAZL, we isolated and characterized the mouse Dazap1 gene, and studied its expression and the subcellular localization of its protein product.

Results: The human and mouse genes have similar genomic structures and map to syntenic chromosomal regions. The mouse and human DAZAP1 proteins share 98% identity and their sequences are highly similar to the Xenopus orthologue Prrp, especially in the RBDs. Dazap1 is expressed throughout testis development. Western blot detects a single 45 kD DAZAP1 protein that is most abundant in the testis. Although a majority of DAZAP1 is present in the cytoplasmic fraction, they are not associated with polyribosomes.

Conclusions: DAZAP1 is evolutionarily highly conserved. Its predominant expression in testes suggests a role in spermatogenesis. Its subcellular localization indicates that it is not directly involved in mRNA translation.

Figure 3: Developmental expression of Dazap1 and Dazl in mouse testes. RT-PCR was performed on total testicular RNAs isolated from day 15 (El 5) and day 17 (El 7) embryos, new born mice (Day 0), and mice at various days after birth. Wv/Wv testes contain diminished germ cell population due to a mutated W (White spotted) gene. GC1 and MT4 are mouse germ cell and Sertoli cell lines, respectively, and gDNA is mouse genomic DNA. The PCR primers span over introns and produce much larger (if any) fragments from genomic DNA.

Mentions:
Northern analyses of adult mouse tissues showed the presence of two Dazap1 transcripts of 1.75 kb and 2.4 kb, respectively (Figure 2). Only the shorter transcript has been isolated in cDNA clones. Dazap1 was expressed most abundantly in the testis, much less in liver, heart and brain, and even less in other tissues. This pattern of expression is similar to that of the human DAZAP1 (14). RT-PCR analyses showed that Dazap1 mRNA was already present in fetal testes at embryonic day 15, similar to Dazl1 mRNA (Figure 3). The expression of both Dazl1 and Dazap1 persisted throughout testes development, in both the prenatal and postnatal periods. Dazl1 and Dazap1 transcripts were also present in the testes of Wv/Wv mutant mice which contained diminished number of germ cells [18]. However, only Dazap1 was expressed in a mouse germ cell line GCl-spg [19] and a Sertoli cell line MT4. The results suggest that Dazap1 is expressed in both somatic and germ cells in the testis.

Figure 3: Developmental expression of Dazap1 and Dazl in mouse testes. RT-PCR was performed on total testicular RNAs isolated from day 15 (El 5) and day 17 (El 7) embryos, new born mice (Day 0), and mice at various days after birth. Wv/Wv testes contain diminished germ cell population due to a mutated W (White spotted) gene. GC1 and MT4 are mouse germ cell and Sertoli cell lines, respectively, and gDNA is mouse genomic DNA. The PCR primers span over introns and produce much larger (if any) fragments from genomic DNA.

Mentions:
Northern analyses of adult mouse tissues showed the presence of two Dazap1 transcripts of 1.75 kb and 2.4 kb, respectively (Figure 2). Only the shorter transcript has been isolated in cDNA clones. Dazap1 was expressed most abundantly in the testis, much less in liver, heart and brain, and even less in other tissues. This pattern of expression is similar to that of the human DAZAP1 (14). RT-PCR analyses showed that Dazap1 mRNA was already present in fetal testes at embryonic day 15, similar to Dazl1 mRNA (Figure 3). The expression of both Dazl1 and Dazap1 persisted throughout testes development, in both the prenatal and postnatal periods. Dazl1 and Dazap1 transcripts were also present in the testes of Wv/Wv mutant mice which contained diminished number of germ cells [18]. However, only Dazap1 was expressed in a mouse germ cell line GCl-spg [19] and a Sertoli cell line MT4. The results suggest that Dazap1 is expressed in both somatic and germ cells in the testis.

Bottom Line:
Although a majority of DAZAP1 is present in the cytoplasmic fraction, they are not associated with polyribosomes.Its predominant expression in testes suggests a role in spermatogenesis.Its subcellular localization indicates that it is not directly involved in mRNA translation.

Background: DAZAP1 (DAZ Associated Protein 1) was originally identified by a yeast two-hybrid system through its interaction with a putative male infertility factor, DAZ (Deleted in Azoospermia). In vitro, DAZAP1 interacts with both the Y chromosome-encoded DAZ and an autosome-encoded DAZ-like protein, DAZL. DAZAP1 contains two RNA-binding domains (RBDs) and a proline-rich C-terminal portion, and is expressed most abundantly in the testis. To understand the biological function of DAZAP1 and the significance of its interaction with DAZ and DAZL, we isolated and characterized the mouse Dazap1 gene, and studied its expression and the subcellular localization of its protein product.

Results: The human and mouse genes have similar genomic structures and map to syntenic chromosomal regions. The mouse and human DAZAP1 proteins share 98% identity and their sequences are highly similar to the Xenopus orthologue Prrp, especially in the RBDs. Dazap1 is expressed throughout testis development. Western blot detects a single 45 kD DAZAP1 protein that is most abundant in the testis. Although a majority of DAZAP1 is present in the cytoplasmic fraction, they are not associated with polyribosomes.

Conclusions: DAZAP1 is evolutionarily highly conserved. Its predominant expression in testes suggests a role in spermatogenesis. Its subcellular localization indicates that it is not directly involved in mRNA translation.